FreeBSD Manual Pages

IOSTAT(8) FreeBSD System Manager's Manual IOSTAT(8)
NAMEiostat -- report I/O statistics
SYNOPSISiostat [-CdhIKoTxz?] [-ccount] [-Mcore] [-ndevs] [-Nsystem] [-ttype,if,pass] [-wwait] [drives]
DESCRIPTION
The iostat utility displays kernel I/O statistics on terminal, device and
cpu operations. The first statistics that are printed are averaged over
the system uptime. To get information about the current activity, a
suitable wait time should be specified, so that the subsequent sets of
printed statistics will be averaged over that time.
The options are as follows:
-c Repeat the display count times. If no repeat count is specified,
the default depends on whether -w is specified. With -w the
default repeat count is infinity, otherwise it is 1.
-C Display CPU statistics. This is on by default, unless -d or -x is
specified.
-d Display only device statistics. If this flag is turned on, only
device statistics will be displayed, unless -C or -T is also speci-
fied to enable the display of CPU or TTY statistics.
-h Put iostat in `top' mode. In this mode, iostat will show devices
in order from highest to lowest bytes per measurement cycle.
-I Display total statistics for a given time period, rather than aver-
age statistics for each second during that time period.
-K In the blocks transferred display (-o), display block count in
kilobytes rather then the device native block size.
-M Extract values associated with the name list from the specified
core instead of the default ``/dev/kmem''.
-n Display up to devs number of devices. The iostat utility will dis-
play fewer devices if there are not devs devices present.
-N Extract the name list from the specified system instead of the
default ``/boot/kernel/kernel''.
-o Display old-style iostat device statistics. Sectors per second,
transfers per second, and milliseconds per seek are displayed. If
-I is specified, total blocks/sectors, total transfers, and mil-
liseconds per seek are displayed.
-t Specify which types of devices to display. There are three differ-
ent categories of devices:
device type:
da Direct Access devices
sa Sequential Access devices
printer Printers
proc Processor devices
worm Write Once Read Multiple devices
cd CD devices
scanner Scanner devices
optical Optical Memory devices
changer Medium Changer devices
comm Communication devices
array Storage Array devices
enclosure Enclosure Services devices
floppy Floppy devices
interface:
IDE Integrated Drive Electronics devices
SCSI Small Computer System Interface devices
other Any other device interface
passthrough:
pass Passthrough devices
The user must specify at least one device type, and may specify at
most one device type from each category. Multiple device types in
a single device type statement must be separated by commas.
Any number of -t arguments may be specified on the command line.
All -t arguments are ORed together to form a matching expression
against which all devices in the system are compared. Any device
that fully matches any -t argument will be included in the iostat
output, up to the number of devices that can be displayed in 80
columns, or the maximum number of devices specified by the user.
-T Display TTY statistics. This is on by default, unless -d or -x is
specified.
-w Pause wait seconds between each display. If no wait interval is
specified, the default is 1 second.
The iostat command will accept and honor a non-integer number of
seconds. Note that the interval only has millisecond granularity.
Finer values will be truncated. E.g., ``-w1.0001'' is the same as
``-w1.000''. The interval will also suffer from modifications to
kern.hz so your mileage may vary.
-x Show extended disk statistics. Each disk is displayed on a line of
its own with all available statistics. If this flag is turned on,
only disk statistics will be displayed, unless -C or -T is also
specified to enable the display of CPU or TTY statistics.
-z If -x is specified, omit lines for devices with no activity.
-? Display a usage statement and exit.
The iostat utility displays its information in the following format:
tty
tin characters read from terminals
tout characters written to terminals
devices
Device operations. The header of the field is the device name and
unit number. The iostat utility will display as many devices as
will fit in a standard 80 column screen, or the maximum number of
devices in the system, whichever is smaller. If -n is specified on
the command line, iostat will display the smaller of the requested
number of devices, and the maximum number of devices in the system.
To force iostat to display specific drives, their names may be sup-
plied on the command line. The iostat utility will not display
more devices than will fit in an 80 column screen, unless the -n
argument is given on the command line to specify a maximum number
of devices to display. If fewer devices are specified on the com-
mand line than will fit in an 80 column screen, iostat will show
only the specified devices.
The standard iostat device display shows the following statistics:
KB/t kilobytes per transfer
tps transfers per second
MB/s megabytes per second
The standard iostat device display, with the -I flag specified,
shows the following statistics:
KB/t kilobytes per transfer
xfrs total number of transfers
MB total number of megabytes transferred
The extended iostat device display, with the -x flag specified,
shows the following statistics:
r/s read operations per second
w/s write operations per second
kr/s kilobytes read per second
kw/s kilobytes write per second
qlen transactions queue length
svc_t average duration of transactions, in milliseconds
%b % of time the device had one or more outstanding transac-
tions
The old-style iostat display (using -o) shows the following statis-
tics:
sps sectors transferred per second
tps transfers per second
msps average milliseconds per transaction
The old-style iostat display, with the -I flag specified, shows the
following statistics:
blk total blocks/sectors transferred
xfr total transfers
msps average milliseconds per transaction
cpu
us % of cpu time in user mode
ni % of cpu time in user mode running niced processes
sy % of cpu time in system mode
in % of cpu time in interrupt mode
id % of cpu time in idle mode
FILES
/boot/kernel/kernel Default kernel namelist.
/dev/kmem Default memory file.
EXAMPLES
iostat -w 1 da0 da1 cd0
Display statistics for the first two Direct Access devices and the first
CDROM device every second ad infinitum.
iostat -c 2
Display the statistics for the first four devices in the system twice,
with a one second display interval.
iostat -t da -t cd -w 1
Display statistics for all CDROM and Direct Access devices every second
ad infinitum.
iostat -t da,scsi,pass -t cd,scsi,pass
Display statistics once for all SCSI passthrough devices that provide
access to either Direct Access or CDROM devices.
iostat -h -n 8 -w 1
Display up to 8 devices with the most I/O every second ad infinitum.
iostat -dh -t da -w 1
Omit the TTY and CPU displays, show devices in order of performance and
show only Direct Access devices every second ad infinitum.
iostat -Iw 3
Display total statistics every three seconds ad infinitum.
iostat -odICTw 2 -c 9
Display total statistics using the old-style output format 9 times, with
a two second interval between each measurement/display. The -d flag gen-
erally disables the TTY and CPU displays, but since the -T and -C flags
are given, the TTY and CPU displays will be displayed.
SEE ALSOfstat(1), netstat(1), nfsstat(1), ps(1), systat(1), devstat(3), gstat(8),
pstat(8), vmstat(8)
The sections starting with ``Interpreting system activity'' in InstallingandOperating4.3BSD.
HISTORY
This version of iostat first appeared in FreeBSD 3.0.
AUTHORS
Kenneth Merry <ken@FreeBSD.org>
BUGS
The use of iostat as a debugging tool for crash dumps is probably limited
because there is currently no way to get statistics that only cover the
time immediately before the crash.
FreeBSD 9.2 November 24, 2010 FreeBSD 9.2